From b0dce103daac406064d7720a83bb467bd65cd53a Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.org>
Date: Thu, 14 Jun 2018 11:21:04 +0100
Subject: [PATCH] irqchip: irq-bcm2835: Calc. FIQ_START at boot-time

ad83c7cb2f37 ("irqchip/irq-bcm2836: Add support for DT interrupt polarity")
changed the way that the BCM2836/7 local interrupts are mapped; instead
of being pre-mapped they are now mapped on-demand. A side effect of this
change is that the call to irq_of_parse_and_map from armctrl_of_init
creates a new mapping, forming a gap between the IRQs and the FIQs. This
 gap breaks the FIQ<->IRQ mapping which up to now has been done by assuming:

1) that the value of FIQ_START is the same as the number of normal IRQs
that will be mapped (still true), and

2) that this value is also the offset between an IRQ and its equivalent
FIQ (which is no longer the case).

Remove both assumptions by measuring the interval between the last IRQ
and the last FIQ, passing it as the parameter to init_FIQ().

Fixes: https://github.com/raspberrypi/linux/issues/2432

Signed-off-by: Phil Elwell <phil@raspberrypi.org>
---
 drivers/irqchip/irq-bcm2835.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/irqchip/irq-bcm2835.c
+++ b/drivers/irqchip/irq-bcm2835.c
@@ -74,8 +74,6 @@
 #define NR_BANKS		3
 #define IRQS_PER_BANK		32
 #define NUMBER_IRQS		MAKE_HWIRQ(NR_BANKS, 0)
-#undef FIQ_START
-#define FIQ_START		(NR_IRQS_BANK0 + MAKE_HWIRQ(NR_BANKS - 1, 0))
 
 static const int reg_pending[] __initconst = { 0x00, 0x04, 0x08 };
 static const int reg_enable[] __initconst = { 0x18, 0x10, 0x14 };
@@ -203,7 +201,7 @@ static int __init armctrl_of_init(struct
 				  bool is_2836)
 {
 	void __iomem *base;
-	int irq, b, i;
+	int irq = 0, last_irq, b, i;
 	u32 reg;
 
 	base = of_iomap(node, 0);
@@ -243,6 +241,8 @@ static int __init armctrl_of_init(struct
 		pr_err(FW_BUG "Bootloader left fiq enabled\n");
 	}
 
+	last_irq = irq;
+
 	if (is_2836) {
 		int parent_irq = irq_of_parse_and_map(node, 0);
 
@@ -273,7 +273,7 @@ static int __init armctrl_of_init(struct
 		}
 	}
 #ifndef CONFIG_ARM64
-	init_FIQ(FIQ_START);
+	init_FIQ(irq - last_irq);
 #endif
 
 	return 0;
